Our proposed imaging-based clinical trial is in the field of thoracic radiation oncology where radiation therapy is used to treat lung tumors. We present a new and exciting type of lung function imaging especially suited for radiation oncology that we refer to as '4DCT-ventilation'. We will use the 4DCT-ventilation imaging to perform a functional avoidance radiation therapy clinical trial. Functional avoidance implies optimizing the radiation dose distribution to avoid functional portions of the lung. 4DCT-ventilation measures which areas of the lung are used for breathing and functional avoidance will allow physicians to avoid these areas when delivering radiation. Avoiding functional portions of the lung can substantially reduce side effects and significantly improve quality of life for lung cancer patient receiving radiation therapy. The purpose of our early phase imaging based clinical trial will be to evaluate the safety and efficacy of 4DCT-ventilation functional avoidance. Our hypothesis is that 4DCT-ventilation functional avoidance radiotherapy results in less toxicity when compared to the current standard of care. Lung cancer patients enrolled on our trial will have a functional avoidance plan generated using their 4DCT-ventilation imaging. Patients will undergo a series of pre-treatment and post-treatment lung function evaluation including clinical toxicity endpoints as well as imaging and functional assessments. We will evaluate the safety and efficacy of functional avoidance using clinical end-points and perform treatment assessment using imaging biomarkers. 4DCT-ventilation imaging is a novel imaging technique especially suited for radiation therapy because the imaging is accomplished using data acquired as part of routine clinical care. 4DCT-ventilation imaging does not burden the patient with an extra imaging procedure, reduces the imaging related cost, and spares the patient from any unnecessary radiation exposure. 4DCT-ventilation functional avoidance uses the novel imaging to present a new treatment approach that 'personalizes' radiation therapy to each patient's unique regional lung function profile. Our clinical trial will provide a rigorous, evidence-based study to translat this exciting new treatment technique into clinical care. The retrospective work for 4DCT-ventilation and functional avoidance has been complete. The next logical step is an early phase clinical trial evaluating the safety and efficacy of functional avoidance. Our clinical trial will demonstrate that 4DCT-ventilation based functional avoidance is safe, develop important evaluation metrics, and provide efficacy that will present clear evidence for a large scale randomized study. Our proposed project will personalize thoracic radiation therapy through 4DCT-ventilation imaging and has great potential to improve outcomes and quality of life of lung cancer patients receiving radiation therapy.